Two wire former

ABSTRACT

THE INVENTION RELATES TO THE ART OF FORMING FIBROUS WEBS E.G., PAPER FROM DILUTE AQUEOUS FIBER SUSPENSIONS FED INTO A WEB FORMING ZONE DEFINED BY A PAIR OF OPPOSED POROUS FORMING BELTS OR &#34;WIRES&#34; DRIVEN INTO GRADUAL CONVERGENCE, IN A FORMING ZONE, BY (1) AN OPEN-FACED ROLL WRAPPED BY ONE OF THE BELTS AND (2) AN OPPOSED POROUS STATIONARY GUIDE WRAPPED BY THE OTHER OF THE BELTS AND URGING THE SAME INTO SUCH CONVERGENCE IN THE FORMING ZONE WITH THE ONE BELT, THE STATIONARY GUIDE PRESENTING A NON-CIRCULAR ACTIVE SURFACE DEFINED BY THE LONGITUDINAL CONTOUR OF A PLURALITY OF BELT-CONTACTING LONGITUDINALLY SPACED TRASVERSE EDGES.

June 1, D. R. GUSTAFSON ETAL 3,582,467

' TWO WIRE FORMER Filed June 25, 1968 1 6 Sheets-Sheet 1 INVENTOAS(/0629 f Sofimaeng June 1, 1971 D. R. GUSTAFSON ETAL 3,582,467

" v TWOYWIRE Fomm Filed June 25, 1968' 6 Sheets-Sheet z I I 2 a 25 Z/lNvENr'ORs D. R. GUSTAFSON ETAL 3,582,467

June 1, 197 1 TWO WIRE FORMER 6 Sheets-Sheet 5 Filed June 25, 1968 Fg ZINVENTORS June 1,1971 7 GUSTAFSON El'AL 3,582,467

' TWO WIRE FORMER F led Jun e 2 5. 1968 s Sheets-Sheet 4 INVIIINIURSQDay/ a IQ 6215/0/60 I I June 1, 1971 sus so ETAL 3,582,467

TWO WIRE FORMER Filed June 25, 1968 'e Sheets-Sheet e INVENTORS UnitedStates Patent TWO WIRE FORMER David R. Gustafson and John F. Schmaeng,Rockton, Ill., and John S. Finnila, Kent, Wash., assignors t0 BeloitCorporation, Beloit, Wis. Filed June 25, 1968, Ser. No. 739,796 Int. Cl.D21f 1/00 US. Cl. 162-303 14 Claims ABSTRACT OF THE DISCLOSURE Theinvention relates to the art of forming fibrous webs e.g., paper fromdilute aqueous fiber suspensions fed into a web forming zone defined bya pair of opposed porous forming belts or wires driven into gradualconvergence, in a forming zone, by (1) an open-faced roll wrapped by oneof the belts and (2) an opposed porous stationary guide wrapped by theother of the belts and urging the same into such convergence in theforming zone with the one belt, the stationary guide presenting anon-circular active surface defined by the longitudinal contour of aplurality of belt-contacting longitudinally spaced transverse edges.

The present invention relates to improvements in paper making machineryor the like, and more particularly, to improvements in devices andmethods for forming the initial web of fibrous material from a dilutesuspension in paper machines or the like.

Although the instant invention is particularly adapted for use in theforming arrangement of paper making machinery and it will be describedprimarily in connection therewith, it will be appreciated that theinvention has other uses in related devices. Essentially, the inventionis concerned with a new and unique forming arrangement which has beendevised for such purposes as accommodating higher paper making machineryspeeds as well as improved quality in the paper so made. It will beappreciated that the very substantial capital investment in paper makingmachinery makes it necessary for continuous research and development inimprovements in not only paper making quality but operating speeds forsuch machinery. The instant invention provides a novel arrangement andmethod for effecting improved paper making quality at high speeds.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

ON THE DRAWINGS FIGS. 1A and 1B represent side elevational views shownin longitudinal succession or sequence of a paper forming sectionembodying the instant invention, and it will be appreciated that thesetwo views may be referred to as a single embodiment of the overallforming unit;

FIG. 2 represents in side elevation, with certain parts shown insection, an enlarged inlet and forming zone arrangement for use in theembodiment of FIGS. 1A and 1B;

FIG. 3 represents a side elevational view of an alternate couch sectionfor use with the embodiment of FIGS. 1A and 1B; and

FIGS. 4A and 4B represent a side elevational view, in longitudinalsuccession A-B, of still another embodiment of the invention.

AS SHOWN ON THE DRAWINGS In FIGS. 1A and 1B there is shown a firstforming wire loop 11 that is wrapped about guide rolls including therolls 12 and 13 shown within the loop of the wire 11 "ice in FIGS. 1Aand 1B, although it is apparent that the loop of the wire 11 is shown tobe extending beyond the right hand side of the view of FIG. 1B(obviously with other guide rolls which are not shown) and coming backalong a lower return run around a forward tensioning roll 13. The roll13 is adjustable as indicated by the double-headed arrow 13A mountingthe same on bearings on a lower horizontal framing Hl, which tensioningroll 13 may be used to apply the desired tension to the forming wireloop 11 during operation in a manner that is substantially conventionalfor the use and function of forming wire tensioning rolls. In FIG. IE,it will be noted that the essentially horizontal frame Hl is providedwith a pair of essentially vertical frame members V-l and V-2 whichextend upwardly to mount successively a second horizontal frameprojection H2, and a third and fourth essentially horizontal frame H3and H4, again in generally conventional supporting structure. The guideroll 12 for the wire 11 is shown essentially schematically mounted forrotation on the upright frame member V2.

A second forming wire 21 is also shown in FIG. 1B mounted on a pluralityof guide and tensioning rolls which are shown mounted for rotation,respectively, at 22 on the framing projection H2; and at 23, 24 and 25appropriately mounted on bearings which are in turn mounted on the tophorizontal frame H-4, again in essentially conventional manner whichneed not be described in further detail herein. It will be noted,however, that the positioning screw 22a on the framing upright V-1assists in positioning the roll 22 and tensioning of the wire loop 21 isafforded by adjustable mounting devices shown for the rolls 23 and 24,both of which devices are represented schematically by two-headed arrowsat 23a and 24a, respectively. The first mentioned forming wire 11 andthe second mentioned forming wire 21 shown in FIGS. 1A and 1B are thusmounted with appropriate, although conventional, guide and tensioningmeans for effecting the desired tension control thereof and, althoughnot shown specifically, drive means are provided, e.g., for the rolls 12and 23, 24, 25, so that the actual peripheral or longitudinal machinedirection speeds of the two wires 11 and 21 are controllable and arecoordinated, again in conventional manner, for the purposes hereinafterdescribed. Guide and tensioning means for forming wires generally arewell known and need not be further described herein.

It will be noted, however, that the forming wire 21 is also wrappedabout a large diameter open roll designated 26 (FIG. 1B), over asubstantial suction area indicated essentially diagrammatically at 26athereof, and is provided with an off-running saveall 26b extendinggenerally upward in the view of FIG. 1B from close running relation tothe surface of the open roll 26 at approximately the cross-machine lineof separation of the forming wire 21 from the periphery thereof, so thatdroplets of water tending to be retained in the periphery of the openroll 26 may be thrown into such saveall 26b and not back against theinner periphery of the forming wire 21.

It will also be noted that the first mentioned forming wire 11approaches the open faced roll 26 (wrapped by the second mentioned wire21) over a wire guide device 15 (which will be described in greaterdetail hereinafter) which acts against the inner periphery of the loopof the wire 11 to control the position of the wire 11 as it travelsthereover and also to control its position relative to its spacing fromthe second mentioned wire 21 wrapped about the open roll 26 at acritical web-forming zone between the wires 11 and 21 at the upstreamend 26aa of the suction area for the open roll 26. Immediately after theposition controlling box or device 15 for the wire 11, in itslongitudinal or machine direction travel, it well be seen that the wire11 continues in its direction of travel under tension as What might becalled a free loop for a short distance of travel before it appears, inFIG. IE, to be wrapped about and on the second Wire 21 that is beingcarried on the outer periphery of the open roll 26 opposite the overallsuction area 26a thereof. Actually, it is apparent from FIG. 1B thatthere is an initial convergence between the Wires 11 and 21 that iscontrolled by the substantially unyielding periphery of the open roll 26and the substantially unyielding elements of the guide box 15 (in aninitial forming zone region designated X-l) after which the forming wire21 continues to travel on the outer periphery of the open roll 26 whilethe opposed forming wire 11 travels in the substantial absence ofrestraining contact through a terminal forming zone portion indicated atX-'2 in FIG. 1B. The overall webforming zone is represented as the totalperipheral dimension of X-l plus X-2 in FIG. 1B, after which the initialor insipient web is formed in essentially a sand wich-type structurebetween the wires 11 and 21 and continues to travel around a substantialadditional portion of the periphery of the open roll 26, opposite anadditional portion of the suction area 26a thereof.

To recapitulate, then, the forming wire 21 is caused to travel in asubstantially unyielding course of travel against and around theperiphery of the open roll 26 through the forming area, which incomposite may be referred to as X, and afterwards until approximatelythe off-running suction sealing strip 260 and the saveall 26b adjacentthereto; whereas the opposed forming wire 11 travels under tension andwith controlled spacing from the opposite forming wire 21 over the box15 for an initial peripheral forming zone region X1, then as a yieldingbut tensioned free loop through a second forming zone portion X-2, andfinally in the aforesaid sandwich structure for the remainder of thesuction area X 3 of the open roll 26.

Essentially the wire guide and control box 15 shown in FIG. 1B functionsto effect a desired and quite precise positioning of the wire 11 andspacing of the same from the Wire 21 during an early and very criticalportion of the forming zone X-l, and it will be appreciated that thisconcept of control of the positioning of the outer wire 11 in the earlystages of the forming zone X-l is of particular significance in theoperation of the instant forming zone, not only from the point of viewof affording considerable flexibility in adjusting water drainage ratiosthrough the wire 11 as against through the wire 21 and into the interiorof the roll 26, but also control as to the incremental pressuredifferences that might otherwise tend to be created against the stock inthe forming zone X-l and also X-2 at this extremely significant regionof web formation.

It will be appreciated that, particularly in the case of the formationof paper 'webs from stocks of various concentrations, the rate ofdeposition of the stock fibers onto the opposed wires 11 and 21 at thevery initial forming zone region X-l creates a fiber bed on each ofthese two wires that will function only generally like a filter bed. Infiltration, the filter aid often used has definite drainagecharacteristics, particle sizes, and even particle orientation so thatits rate of drainage relative to its thickness is often believed to be afunction that can be calculated, or at least many skilled workers in theart pretend to be able to calculate the same. Filter aids and materialsbeing filtered have been studied for the purpose of making suchcalculations and some degree of uniformity is ordinarily sought in thisrespect.

Studies have been made in connection with the deposition of fibers frompaper making stock onto a wire in an effort to correlate the academicprinciples and concepts thereof with those of filtration calculations,but for a number of different reasons these calculations proved to beprimarily approximations rather than something in the nature of exactpredictions. Paper stock fibers are not identical in size and shape andthis serves to be particularly complicating in this situation, sincecertain filter aids may often be selected in such a way that their sizeand shape characteristics can be controlled. With paper web formation,it is perhaps particularly significant to note that the object is notthat of protecting some sort of exact control on the bases of the typesof uniformity which might be used in filtration calculations, becausethe felting of a paper web of a multiplicity of particle sizes (plus amultiplicity of additives such as clay and the like which really bear nophysical resemblance to fibers of various sizes in the paper machinestock) serve to substantially defy intelligent and predictablecalculation. It is also understood that the cellulosic fibers of theusual paper machine stock actually have a certain amount ofsemi-chemical solva tion characteristics in retention of water moleculesand the like, so that the notion of predictable calculations relativethereto may be attractive and the subject of a number of academicefforts on the part of the skilled workers in the art; but it can hardlybe denied that the actual problems of practice in connection With webformation are instead very deceptive. Additionally, the paper machinestock is known to have properties that are not consistent with theclassic Newtonian fluid flow properties by virtue of the suspendedmatter therein, so that translation of high speed machine directionstock jets to stock bodies under pressure exerted more or less in thenormal direction to the machine direction represents still another phaseof the complications here involved.

The instant invention is based upon certain discoveries which are notrepresented as solving the academic problems which have frustratedworkers in the art over the years. Instead, the instant inventionaffords certain significant aspects of versatility in the forming zoneoperation which make it possible for the operator to adjust the papermachine forming zone to various stock characteristics, within quitebroad but reasonable limits, while at the same time affording uniquelypracticable and functional operation.

With respect to the functional and practical aspects of the instantinvention, attention is directed to the fact that he formingwire 21 iscarried substantially entirely by comoving functional parts, includingparticularly the open roll 26 which travels at a peripheral speed thatis matched with the desired peripheral speed of the longitudinallymoving forming wire 21. In addition, the forming Wire 11 also travelssubstantially over co-moving guide and tensioning devices which, as inthe case of the wire 21, serve to minimize wear on the wire and servegenerally to add substantially to the practical aspects of the operationof the instant paper making machine, and particularly the function ofthe forming zone therein.

It will be seen, however, that there are certain elements in thepositioning and guiding control box 15 which are stationary and overwhich the forming wire 11 travels; but these elements offer uniqueadvantages in the instant device in that they provide a substantialminimum number of wire contacting surfaces and/or a minimum area of wirecontacting surface with respect to which there is in fact relativemovement between the rapidly traveling wire 11 and the stationaryelements of the box 15. Also, it will be appreciated that the wirecontacting elements in the box 15, which will be defined in greaterdetail hereinafter, are preferably provided with substantiallyfrictionless wire contacting surfaces in the form of such surfaces asextremely hard, refractory and smooth (micro-finish) elements which willin fact minimize wear on the wire 11. The nature and character of suchrefractory ceramic types of surfaces has already been described indetail and does not require additional description herein.

Referring to FIG. 2, it will be seen that FIG. 2 shows an enlargement ofthe essential features of the forming area here involved. Thus,referring to FIG. 2, it will be noted that the upstream sealing strip26d is shown positioned at approximately (or slightly upstream of) theslice exit (which is here designated by the dimension H The forming zoneportion X-l which is defined by the wire 21 wrapping the outer peripheryof the open roll 26 and the wire 11 wrapping the functional wire guidesurfaces of the box is shown as having diminishing thickness from theslice jet dimension H to an intermediate dimension H over a distancedesignated D Actually the overall initial forming zone region X-l inwhich both wires 11 and 21 are being guided into convergence is longerthan the intermediate dimension D which is used for reference in FIG. 2,since the guided convergent zone X-l terminates approximately at thebeginning of the forming zone X-2 which is defined by the wire portion11a at the off-running side of the box 15 which is itself free fromrestraining support contact for the peripheral dimension indicated inFIG. 2. Without elaborating upon the particular longitudinal alignmentof the stock jet centerline CL indicated in FIG. 2, being fed from thestock jet inlet designated generally I, it will be sufficient to notethat the approximate thickness of the stock jet that is fed out of theinlet device I is designated H and after the stock has traveled therelatively short distance D the overall thickness of the stock in theinitial forming zone X-l has diminished to the dimension indicated at Hby virtue of the desired rapid drainage into the suction area 26aa ofthe open roll 26 and downwardly between the blades or foils 15a through15c, alphabetically, of the guide box 15. The open roll 26 may have anumber of conventional constructions, which are not per se novel in theinstant arrangement. As here shown, the open roll 26 is provlded with anouter shell 26 with perforations indicated partly at 26g, to providestructural strength thereto. The outer portion of the shell 16 may beprovided with honeycomb cells or simply a plurality of cross-machineradial extensions here indicated at 26h, and about which a surfacescreen or wire of spiral configuration (not shown) is ordinarilyemployed to uniformly support the travellng forming wire here designatedonly by the line 21. In short, the open roll 26 does not providesubstantlal land areas backing against the forming wire 21 which wouldtend to effect the formation of pressure differentials on the inside ofthe loop of the wire 21 opposite the formlng zone regions X-l, X-2, oreven the subsequent dewatering region X-3, but the screen or spiral wirecovered fins 26h are mounted essentially for structural support for theforming wire 21, in an open roll arrangement of generally conventionalstructure. The sealing strip 26d and its downstream counterpart 260(FIG. 1B) are connected to a conventional pressure control gland that 1scoaxially mounted within the open roll shell 26 and is equipped byconventional means which need not be described herein for maintenance ofa desired, generally subatmospheric pres sure between these glands 26dand 260 over the various zones X-l, X-2 and X3 already described. Withthe woven forming wire 21 (which may be formed of plastic or syntheticresin (e.g. nylon) fabric) mounted on the outer periphery of the openroll 26 is thus malntained throughout the forming zone regions justdescribed with a substantially uniform pressure (i.e. subatmosphericpressure) so that there is continuously maintained at such forming wire21 (on both the inner periphery anl outer periphery as a practicalmatter) a predetermined pressure that is essentially constant for themore critical reglons of the forming zone and which is controlled as apractlcal matter quite readily simply by controlling the pressure wtihinthe suction gland between the sealing strips 26c and 26d. Thus, the rateof drainage from the stock issuing from the jet I and flowing throughthe forming wire 21 into the interior of the open roll 26 isfunctionally controlled. Moreover, the pressure control arrangement justdescribed is functionally adequate to maintain a substantially uniformpressure continuously along the inner periphery of the forming wire 21during the initial forming zone peripheral region X-l, and thesubsequent forming zone region X-2, and/or the subsequent dewateringzone X-3, primarily on the basis of known operating controls in papermachines. The functional capability of the open roll 26 to perform inthis manner is understood by those skilled in the art. It will beappreciated, however, that by relative tilting of the stock jet device Iso that the centerline C] of the stock jet may be tilted relative to anapproximate tangent to the open roll 26 is also used to assist in theactual control of the amount of drainage through the wire 21 anl intothe interior of the open roll 26. Again, this is a concept which theskilled worker in the art can readily appreciate.

With respect to the instant invention, however, the additional variable,which is now controllable, involves the gontrlosl of drainage in theopposite direction through the Starting with an initial assumption thateach of the blade elements 15a through 15e, alphabetically, is actuallypositioned in the manner desired for a given operation of a papermachine in the forming zone, it must be appreciated that the element 15ais primarily a member for guiding the wire 11 into an appropriateapproach to the initial and critical forming zone area X-l; but theimmediately subsequent blades 15b through 156, alpphabetically, arepositloned in FIG. 2 with their top surfaces extending transversely ofthe machine direction. These top surfaces for the elements 15b through1512, alphabetically, are actually quite narrow in the longitudinaldimension and they are spaced longitudinally a relatively substantialdistance (at least in relation to the longitudinal dimension of theirtop surfaces). In fact, the preferred open area for the box 15 isordinarily at least 50% and in the practical embodiments of theinvention presently recognized something in the nature of 60 toaveraging perhaps about 75% open area. The blades 15b through 15c,alphabetically, are formed so as to effect substantially a cross-machineor transverse line contact with the traveling wire 11. The less surfacecontacting the wire 11, essentially the less wear on the wire 11. Ofcourse, since the stock jet itself will be issuing at the locationindicated at H under considerable pressure (by virtue of high speed jetvelocities in the nature of 2000, 3000 or perhaps 3500 or more feet perminute) this very high speed stock jet tends to develop substantialpressures in the stock that is being driven into a zone of convergencewherein the apparent volume is being diminished very rapidly at theoperating speeds here involved. Of course, drainage of the stock throughthe Wires 11 an 21 accommodates this rapid diminution of the apparentforming zone volume, but the drainage must necessarily occur by forcingthe water in the stock through the dispersed stock solids of fiber,clay, etc. which build up rapidly on each of the wires 11 and 21 andafford resistance. Accordingly, the stock jet speed in translated intopressure that is generally normal to the tangent of the wire wrappedopen roll 26 and, of course, the tangent of the guided wire 11. Theguided wire 11 moves under relatively high tension so that it will notbe depressed by such pressure in the open areas between the blades 15athrough 15c, alphabetically, but it is apparent that by the use of hightension effective to avoid this relatively undesirable result the wire11 does not really travel through a true curve over the blades 15::through 1542. Instead, it travels through a plurality of chords from theapproximate line of contact at the top of each of these blades 15bthrough 15c, alphabetically, t0 the next approximate line of contact.The more tension that is applied to the wire 11, the more closely thewire 11 will assume the configuration of a plurality of chords passingfrom one blade to the next in the box 15. It is also apparent, however,that the longitudinal or machine direction profile or contour of thelocii of such multiplicity of relatively closely longitudinally spacedporous belt or wire 11 contacting generally transverse edges 1512through 15e, alphabetically, will be a curve. It is conceivable thatunder a certain set of unique circumstances the operating conditionswithin the forming zone X-1 might call for substantially a co-planarcontour of such wire contacting edges, particularly if the diameter ofthe open roll 26 were extremely great in size. But this could only beapproximately co-planar, because the mathematics of the drainage curves(to the extent that the same can be intelligently represented), do notcall for a straight line function. Thus the mathematics here involvedcall for a relationship between the spacing between the wires 11 and 21,which is shown at the slice outlet to be H as a function of thelongitudinal or downstream distance of the stock, which distance is hererepresented in a specific instance as D to reach a spacing between thewires that is designated H in the instant FIG. 2, for purposes ofexample.

With respect to the mathematics here involved, those skilled in the artwill recognize that a general evaluation may be possible on the basis ofthe teachings already set forth herein, although it is hardly possibleto expect a formula which will offer the solution for all types of stocksimply by elementary arithmetic. Thus the formula for the relationshipbetween the spacing between the wires 11 and 21 as a function of thedownstream dimension from the slice outlet may best be represented bythe following formula: H CD wherein H is the distance in inches betweenthe wires (i.e. the wires 11 and 21 FIG. 2), D is the distance in incheslongitudinally or downstream from substantially th point of introductionof the stock jet between the wires (i,e, here shown to be substantiallyat H C is a constant which for the preferred thin channel jet issubstantially 0.5 (although it may range over the practical jetthickness dimension from perhaps slightly less than 0.5, i.e. for usualcircumstances involving 0.25 or 0.3 jet stream thicknesses to thickerjet streams of l to 1.5 or more which might be used). The exponent k isa negative fraction of preferably about preferably but also could rangefrom slightly lower, i.e., O.2 to relatively higher with the thicker jetstreams, i.e. 0.8. As an exemplary calculation, it will be recognizedthat H would change negligibly in approximately the first one inchdownstream:

H=0.5 jet thickness (inch) :0.5 preferred D=1 inch but the criticalaspects of this formula are involved in determining the spacing H overthe range of D=from 1 to 8 to 12 inches.

It will be appreciated that the formula just used more or less assumesthe longitudinal contour of a curve for the wire 11 passing over theblades 15b through 15e, alphabetically, even though this is obviouslynot the case when one considers the nature of the plural chordlikeconfiguration of the wire 11 passing over the blades in the box 15.Also, further study of this formula will reveal that it does notactually require that the wires 21 and 11 will converge through opposedconvex configurations, except in situations in which the diameter of theopen roll 26 is extremely great. Essentially, the curve defined by thelongitudinal contour of the locii of points of contact between theblades 15b, etc. and the wire 11 is one which will correlate therecognized variables such as drainage rate (and particle characteristicswhich cause variations therein), machine speed, stock concentration,overall jet direction, volume and speed, etc. The correlationrepresented by the instant formula is an unusually adequate guide,however, for a determination of the rate of convergence should beeffected between the wires 11 and 21. This rate of convergence in theinitial and critical forming zone X1 is not left to chance, nor is itleft to such things as tension control and the like which ordinarily donot turn out to be satisfactory means for maintenance of the correctcritical positioning of the wire 11 in this arrangement. As mentioned,the forming wire 11 may not be in opposed convex relation to the formingwire 21 unless the diameter 8 of the roll 26 is very substantial, butthis does not mean that an essentially straight line function of thetension on the wire 11 will satisfy this formula. Essentially, thetransverse blades of the 15 series are quite narrow longitudinally, withsubstantial longitudinal spacing therebetween to afford minimuminhibition of flow through the Wire 11, It is also apparent from anexamination of the elevational profile of the individual blade elements15b through 15a, alphabetically, that these blades not only presentapproximately a transverse line of contact with the traveling wire 11but they also present a very abrupt off-running edge or separation fromthe wire 11 so that there will not be pumping effect at the off-runningside of such blades, as there would be in the case of the socalledconventional paper machine foil element P which is designed with a verylimited angle of approximately 3 to 5 off-running taper. Such a pumpingetfect would necessarily cause pressure differentials to be' created atthe immediate underside of the traveling wire 11 as it passes over thebox 15. In particular, it is an important concept of the instantinvention to strive for the maintenance of substantially uniformpressures on the back side of not only the converging wire 11 but alsothe converging wire 21. In this way the initially forming paper web,which is very sensitive to any type of disturbance in the early stagesof its formation, will not be disturbed by any abrupt pressure changesexerted thereagainst from the inner periphery of the forming wires. Theblades 151) through 15c are functional essentially as guides forpositioning the wire 11 in precisely the manner desired. In fact, suchpositioning of the forming wire 11 traveling thereover is doneessentially to correlate such factors as the rate of drainage and thedrainage resistance provided by the earliest stages of web formation onthe outer peripheries of the two wires 11 and 21, such that thetranslation of the relatively high machine direction or longitudinaldirection velocity into pressures with in the stock body in the formingzone X1 will not be afforded an opportunity to undergo fluctuation orvariation, if at all possible. Instead, the desired here is to carry outthis phase of initial web formation by subjecting an increasing webbuildup (even though of very thin and delicate nature) on each of theforming Wires in this critical forming area by continuously and withoutinterruption or varation subjecting these delicate earlyformed webelements to a predetermined pressure.

Considering next the very important matter of bringing about convergencebetween the two wires so that disproportionately greater drainings willnot occur in only one direction, it will be noted from FIG. 2 that thebox 15 is mounted on a fixed pivot P actuatable by the arm 17 which isin turn connected to the upstream end of the box 15 at a second pivot PThis is essentially a simplified showing of a control aspect which canbe varied to suit the purpose of the operator. A slight tilting of thebox 15 will, of course, cause a definite change in the previouslyexpressed constants C and k in the formula relative to the spacing, forobvious reasons. Except for the fact that paper making machinery must bemaintained as simple as possible for practical use in the mill, otherknown devices for varying the relative positions of the contacting edgesof the blades 15b through 15e, alphabetically, can be accommodated. Forthat matter, even the rod 17 may be mounted so that it is yieldable to apredetermined pressure that might be generated within the stock jet, oreach of the individual blades 15b through 15e, alphabetically, may alsobe so mounted, so that the actual line pressure exerted against the sameby the wire 11 traveling thereover would be continuously constant. Thus,without attempting to limit the invention to any particular type ofcontrol, it will be noted that a diaphragm 17bb might be used to holdthe box 15 in a position responsive to pressure within the forming zoneX-1 via the arm 17, or the individual transverse blade 15b could bepivotally mounted and actuated in response to a pneumatic diaphargm 15bbfor maintaining the individual operating edge of the blade 15b againstthe underside of the wire 11 at a particular pressure generated withinthe stock jet. Such showings are intended to be only schematic for thepurpose of representing the concept that conventional means for mountingeach of the blades 15b through 15e, alphabetically, are certainlyavialable such that an additional aspect of versatility is afforded inthe box 15 so that the individual operating edges of the blades in thebox may in fact act against the underside of the wire 11 such as topreclude excessive pressure differences within the stock in the formingzone from one transverse blade edge to the next, and so forth. It isappreciated that operativeness of devices of this type in a paper milldepend upon numerous other practical factors, but the essential conceptof the invention provides for positioning of the various blades 15bthrough 152 so that a given paper making stock at specific speeds andother operating conditions may actually be able to exert at leastpractically uniform if not exactly uniform pressures against the formingwire in this critical area and variations of the nature which may causedisturbances in web formation can be avoided by the use of the conceptshere involved.

Of course, the view of FIG. 1A introduces still another importantvariable in the overall concept and that is the ability to vary theactual centerline of the stock jet as it is fed into the criticalregions of the forming zone or zones X-1 and X2, so that there will be areasonable distribution of drainage in the two principal directions.Preferably, the rate of drainage, expressed in a ratio, should not besuch that less than substantially 30% or more than substantially 70%occurs through either one of the wires 11 and 21, and optimum resultsare believed to be obtained by using a substantially 50:50 drainageratio. The overall stock inlet which is shown as J in FIG. 1A isconventional in its overall structure, in that it will deliver a diluteaqueous suspension of entangled co-moving fibers in a ribbon-thin streamexiting from the slice (at H of FIG. 2, for example) at a very highspeed and in a substantially longitudinally unidirectional condition.Such unidirectional condition in this instance is approximatelytangential to the open roll 26 but the selection of very slightvariations from a true tangential direction makes possible very helpfulproportioning of the drainage relative to the two wires 11 and 21 in amanner previously described. Thus, a very slight tilting of the jetcenterline so that it tends to impinge more toward the wire 21 on theopen roll 26 will tend to increase the rate of drainage in thisdirection (which drainage in the arrangement of FIG. 2 is against thepull of gravity, although it is in the direction urged by the suctionbox). The inlet itself is a structure that is already well known andunderstood in the trade, and is further described in detail in suchapplications as Justus and Gustafson Ser. No. 467,664, filed June 28,1965 now Pat. No. 3,382,143, which is incorporated herein by reference.Essentially, the overall inlet arrangement is mounted for the desiredadjustment on conventional means which are here indicated by thedouble-headed arrows designated I l and J Such inlet device isessentially functional for the purpose herein described.

In FIG. 2, however, it will be noted that the inlet is provided with anadditional feature in the form of a pair of transverse top and bottomrelatively stiff but resilient (i.e. relatively hard rubber) elementsclamped in the slice exit end of the inlet device I and designated J-land L2 with metallic sheet support elements designated L3 and J4 foradditional stiffening. Such rubber elements or solid elastomer elementsJ-l and J-2 are positioned at the slice outlet so as to extend forwardinto very close running and sealing relationship with the wires 11 and21, respectively, at the location of the slice jet stream outlet H toeffect a nominal pressure seal with the wires 11 and 21. Such elementsI-1 and J-2 would otherwise feed a free jet stream into the convergencebetween the wires 11 and 21, but in this arrangement shown in FIG. 2these elements effect a seal with the wires 11 and 21 and thus afford anadditional pressurized or hydraulic forming zone at Xl and X2 betweenthe wires 11 and 21, such that superatmospheric pressure may begenerated therein to accelerate drainage without backflow of stock indirections opposite to either of the wires 11 or 21. Practical sealingeffect is obtained from a closerunning spacing of 4 inch from the wires11 and 21 to the elements L1 and J-Z. The essentials of the spacingbetween the wires 11 and 21 permit accelerated drainage by virtue of theadditional hydraulic pressure in the forming zone, which hydraulicpressure is also used much more effectively in this particular instanceby virtue of a generallyy downwardly directed jet centerline C], asshown in FIG. 2. Deckle edges not shown) can, of course, be used to addto the uniform cross-machine pressure maintenance in the forming zone.

It should also be noted that the most critical region of the formingzone here designated X1 is actually controlled by the combination of thesurface of the open roll 26 and the guiding blades of the box 15, butthe terminal portion of the forming zone, designated X2, in FIG. 2 isnot necessarily provided with restraining means in contact with the wire11 on the underside thereof. In this latter forming zone region X2, itwill be appreciated that the most delicate aspects of the web formationhave taken place and the finalization of what may be termed webformation as compared to web drainage which will occur more or lesscontinuously during the remainder of the suction area at X3 will notrequire as delicate a positioning of the outboard forming wire portion11a. In fact, the outboard portion of the forming wire 11a will wrap theopen roll 26 but in a closely spaced condition for a substantialperipheral region before it is brought (by virtue of the tension underwhich it operates) into the so-called sandwich structure holding the webW-l against the inboard forming wire 21 wrapping the open roll 26. Theconcept here involved is that the invention provides criticalpositioning of the wire 11 in only the most critical regions of theforming zone Xl, as contrasted to continued support further downstream.The advantage involved is that the configuration through which the wire11 must go in order to conform to the predetermined curvature requiredfor best formation in the zone X1 is such that a rotary surface or aco-moving surface is neither practical nor ordinarily available to holdthe wire 11 in the position that is here shown as being defined by thelongitudinal contour of the locii of generally transversebelt-contacting edges of the elements 15b through 15e, alphabetically.Because of the ideal configuration for the wire 11 that is desired inthe practice of the instant invention in the critical region of theforming zone Xl, it has been found that a limited number of stationaryblades of minimum total contacting area should be used and suchtransverse lines of contact afforded by the blades of the box 15 arethus held to a minimum for the purpose of minimizing any tendency towardwearing of the wire 11 in this arrangement. Substantially after the lastof these blades 152, it is found that the internal pressures within thepartially dewatered stock appear to be suflicient to effect not only thedesired con-figuration in the free loop of the wire 11a, but therelatively substantial initial web formation which has occurred prior tothe last indicated blade 15e is such that opportunities of damaging theweb being formed thereafter are also minimized and the wire 11 may underreasonable tension forces conform adequately to carry out the remainderof the web formation in this region X-2 so that neither excessive wearof the wire (by inordinate tensions thereon) nor excessive additionalguidance of the wire reach 11a (also tending to cause some wear) arerequired. Under these circumstances, it is possible to strike a balancebetween the positive guidance of the configuration of the wire 11 foroptimum conditions for initial and critical web formation in the zoneX-1 and more reasonable positioning of the tensioned wire loop 11a freefrom contact with restraining surface elements in order to complete thedesired Web formation without risks of damage make possible the overallarrangement here shown. This overall arrangement affords excellent webforming conditions of high quality, while at the same time practicalmachine operation from the point of view of very simple equipment andminimum wear and/or replacement of parts for one reason or another.Additionally, the unique flexibility of operation that is here affordedby the use of a relatively large open roll 26 to afford a substantialportion of the curved configuration of one of the forming wires (i.e.21) which is at least a part of one of the essential aspects of best webformation makes possible the use of the greatly simplified nominaltilting adjustment of the stock =jet inlet J coupled with the verynominal adjustment of the blade box so as to afford the remainder of theelements which have been found to be fundamental to conditions foroptimum web formation at high speeds in accordance with present-dayquality and production requirements.

It will also be noted that an intermediate suction box sealing strip maybe positioned at the location designated 26x in FIG. 2 (at approximatelythe end of the forming zone X-2 and the beginning of the dewatering zoneX3) so that an additional control may be afforded in selective variationof the pressure to be maintained against the inner periphery of the wire21 in the regions X1 and X2, as compared to the selection of a differentback pressure against the inner periphery of the wire 21 in the regionX3.

As earlier indicated, with reference to FIG. 1B, a typical known foilstructure F may be operated in substantially close running relation tothe inner periphery of the wire 11 at the approach of the roll 12. Suchfoil device has a taper at its off-running portions F such as to exertsome additional pumping effect for dewatering against a conventionalsave-all P and the structure of one or more such foils F removed fromthe immediate vicinity of the forming zones X-1 and X-2, is often foundto be quite useful in tending to wipe off droplets which may beaccumulating on the underside of the wire 11 as the overall sandwichstructure of the two wires 11 and 21 with the web W1 therebetweentravels toward the roll 12 indicated in FIG. 1B. It is important tonote, however, that the foil F need not actually contact the undersideof the wire 11, such that it might cause increase operating wear on thewire 11, but such foil structure F may still function to wipe off waterdroplets at its oncoming side F even though the pumping effect of theoff-running side F might be nominal, if minimum wearing of the wire 11by contact with the foil F is desired. In any event, the function of afoil-type structure F such as that here shown, whether or not itactually engages the wire 11, such foil F is positioned preferablysubstantially longitudinally downstream from the periphery of the roll26 and at a location in which parallelism between the runs of wire 11and 21 has already been reached and dewatering of the Web W-l sandwichedtherebet'ween is in process. Thus, the free loop portion 11a of the wire11 at the immediate off-running side of the blade box 15 will stillremain substantially free from any restraining wire contacting meansprior to actual convergence of such free loop 11a into essentialparallelism with the wire 21, at approximately the location 26xindicated in FIG. 2.

Referring briefly to FIG. 3, it will be seen that the embodiment shownin FIG. 3 relates to an alternate travel arrangement for the wirestraveling in parallelism. In FIG. 1B the wires 11 and 21 are separatedat approximately the region of off-running contact over the roll 12. Theroll 12 is preferably a plain roll in FIG. 1B so that it may effectsubstantial retention of the web 'W-l on the off-running wire 11 (whilepermitting ambient atmospheric pressure against the backside of theseparating wire 21 for this purpose).

In FIG. 3, however, the position for the roll 12 is indicated at 32 andthe off-running wires 31 and 41 correspond, respectively, to the wires11 and 21 previously described. In such arrangement, it will be seenthat the wire 31 travels over rolls 32, 33, 34 and 35 (all of whichrepresent traveling wire guides acting against the inner periphery ofthe loop of the wire 31). The top wire 41 is shown moving initially insubstantial parallelism with the bottom wire 31 (and with the webdesignated W3 in FIG. 3) first through a couch press defined by a toproll 42 which is pivotally mounted on an arm 51 with a pressure applyingcoacting means 52 (in the form of a pneumatic cylinder) mounted forapplying pressure between the rolls 33 and 42 at a couch nip N-3, forsome additional dewatering of the web W-3, and followed by separation ofthe top wire 41 as it travels around an additional guide roll 44 andthen back up to a roll 43, which is in substantially the position of theroll 23 of FIG. 1B.

It will also be seen that the horizontal support structures H11 and H-14correspond to extensions of the previ ously designated horizontalsupports H-1 and H-4 of FIG. 1B, and the vertical supports V13 and V-14shown in FIG. 3, plus the depending support V-15, are essentiallyconventional support structure which does not require additionaldescription.

The web W3 is picked off the bottom wire 31 as it travels around a plaincouch roll 34 (which can be an open couch if desired) by a travelingfelt F3 wrapped around a pickup roll designated at 61, which may be aplain pickup roll or a suction pickup roll, depending upon theparticular type of operation contemplated for removal of the web W-3from the bottom wire 31. Essentially, the arrangement of FIG. 3 shows alonger travel path for the wires 11 and 21, or their counterparts 31 and41, in substantial parallelism beyond the roll position 32 and through acouch nip N-3, after which separation of the wires 31 and 41 is effectedin conventional manner.

Referring now to FIG. 4A and 4B, it will be seen that elementscorresponding to some extent to the elements already described insubstantial detail in the previous figures hereof are designated byreference numerals or letters in the series. Thus, it will be seen inFIG. 4A that one of the forming wires 121 wraps a large open faced roll126 having a suction area extending from approximately 126aa (i.e.opposite a slice outlet) to 1260, whereupon the traveling wire 121continues (as shown in FIG. 4B) with the web W-100 thereon over asuction couch roll and along a downwardly inclined wire reach 121 to aplain turning roll 171 and then back over rolls 172 and 173, all asindicated in FIG. 4B. The traveling web W-100 is thus shown as beingremoved by a felt F-300 wrapping a suction pickup r011 161 and urgedagainst the web W100 along the downward incline of the wire run 121. Thefelt F-300 carries the web W-100 along its underside and into a presssection, here shown as comprising a plain roll 181 and a grooved roll182 defining a first press nip PN, pressure forces being applied via athird roll 183. The roll designated 182 in the press section is alsodesignated with G to indicate that it is a grooved roll having thestructure described and claimed for press rolls in E. J. Justus US. Pat.Nos. 3,198,693; 3 ,198,694; 3,198,695; 3,198,696; and 3,198,697.

Also, it will be seen that a type of couch press arrangement with thesuction pickup roll 161 and an opposite adjustably positioned roll 184may be employed, the positioning of the roll 184 being shown asadjustable by virtue of the two-headed arrow at 184a, such that a.nominal pressure at the pickup felt nip FN may be employed, if desiredfor such purposes as improved pickup and dewatering in this immediatelocation.

The guide roll 172 shown in FIG. 4B is also indicated as being pivotallyadjustable by virtue of the two-headed 13 arrow 172a, for purposes ofmaintaining a controlled desired tension on the wire 121.

Referring to FIG. 4A, it will be seen that there is also shown a loopedforming wire 111 traveling over a plurality of co-moving guide rolls1130 through 113g, alphabetically, with the roll 113e functioning as atension control roll adjustably mounted as indicated diagrammatically bythe double-headed arrow 113A. Of course, any of the rolls in the 113series may also be used to cooperate in part as tensioning as well asdrive rolls for the -wire 111 which also travels over a blade box 115,which is functionally comparable in many respects to the blade box ofFIG. 2. The blade box 115 cooperates with the roll 126 in FIG. 4A tomaintain the previously described wire travel spacing (as defined by thepreviously described formula H=CD In the arrangement of FIG. 4A,however, it will be seen that the foil box 115 is provided with a movingpivot P-117 adjustably actuated by conventional jackscrew means 117bb,and swingable about a fixed pivot P-115 mounted on the overall frameworkcomposed of a plurality of generally horizontal supports I-I-121 throughH-126 and a plurality of generally vertically aligned supports V-121through V-130, which horizontal and vertical supports need not bedescribed in greater detail since they are of conventional frameworkstructure.

Referring again to the swingably mounted blade box 115, it will be seenthat refinements in adjustment are also afforded by an additional pivotP-215 and an additional pivotally mounted adjusting device 217bb, suchthat a desired positioning of the active lines of contact for the blades(designated generally at 115a herein for convenience) may be effected inaccordance with the convergence formula previously described and alsoaffording a free wire loop 111a at the immediate off-running side of thelines of contact 115a for the blades 115, essentially in a reversedposition to that shown in FIG. 2 directionwise but in a comparablefunctional arrangement, which need not be described in greater detailherein. The corresponding forming areas are designated X-100, X-200 andX-300, which correspond generally to the previously described suctionareas within the roll 26 as X-1, X2 and X-3, in FIGS. 1B and 2.

It will be appreciated, however, that the roll 126 is shown herein asbeing substantially greater in diameter than its counterpart 26 of FIGS.1B and 2, and it may thus carry out still an additional function in theregion X400, as it holds the 'web W-100 on the wire 121 and effectsseparation of the web W-100 from the opposed traveling wire 111. Forsuch purposes, it will be appreciated that additional suction sealingstrips 126x and 126xx may be mounted in the positions indicated insidethe open roll shell 126 for purposes of effecting different pressurecontrols at different peripheral regions in the travel of the roll 126.

Essentially, there is shown in the roll 126 an initial sealing strip126aa and a sealing strip position 126x at the end of the region X-200,which would comprise the forming zone region at the inner periphery ofthe wire 121. The opposed wire 111 in such region -(i.e. X100 and X 200)travels over the lines of contact 115a of the blade box 115, and thenbriefly through a tensi ned free loop travel 111a for the wire 111during which the tensioned, yielding but free from restraining contactwire region 111a approaches substantial parallelism with the wire 121,converging against the web W-11 sandwiched therebetween.

It will be noted also that the means corresponding to the stock jetdelivering device I already described is designated generally by L100 inFIGS. 4A and 4B and is shown as being mounted for primary adjustment atI (via a turnbuckle-type of adjustment) but also providing or limitedadjustment 1,-100 and at J 100, which adjustable elements willcorrespond essentially to the previously described I l and I for whatamounts to adjustment of the centerline CL of the jet stream that isshown in FIG. 4A as being fed upwardly (at a general incline) andsubstantially tangential to the roll 126. The details of sealing theslice inlet, which are described in detail in connection with theembodiment of FIG. 2, are employed in such upwardly aligned slice inletarrangement for the embodiment J-lOO, but additional description thereofis not necessary, since essentially the purpose is to provide closerunning sealing elements of solid elastomer structure (corresponding toI1 and I-Z) for effecting a pressure sealing of the jet stream as it isfed into a hydraulic forming zone between the converging wires in theregions X100 and X-200.

An additional adjustable feature is controlling the relative ratios ofdrainage between the two wires 121 and 111 is afforded by the compactsuction arrangement S- 115 here shown schematically as being dividedinto partitions 8-1, 5-2, S3, etc., each opposite the longitudinalspacing between a successive pair of lines of contact 115a for theblades in the box 115, so that a selected application of water removalsubatmospheric pressure is possible in each of such longitudinalspacings between the lines of contact 115a. In such arrangement, it is,of course, possible to effect actual pressure differentials from one toanother of the successive longitudinal spacings between the lines ofcontact 115a, should such be desired. It is understood, however, thatpreferably this is not the desired operation for the box 115 and thefunction of the subatmospheric pressurized compartments S1, S-2, etc. isthus to facilitate water removal in a controlled manner by maintenanceof a controlled pressure within each of such compartments of the box5-115 such that the pressure on the incipient web that is forming on theouter periphery of the wire 111 immediately opposite the lines ofcontact 115a may be controlled and preferably maintained substantiallyconstant in this specific region X-100. The suction sealing strip 126awithin the roll 126 will also function in comparable manner to effectwater drainage and pressure control within the open roll 126 to theextent required to maintain a comparable substantially constant pressureagainst the incipient web forming on the outer periphery of the wire 121in the forming region here designated X 100.

In connection with the embodiment of FIG. 4A, it will be appreciatedthat the various control elements for positioning the traveling wires121 and 111 as well as effecting water removal from the innerperipheries thereof may act in a different number of controlledoperations, such that it is possible to maintain what constitutes apractically uniform and substantially non-varying pressure against thefragile initially forming incipient webs within the forming zone X-10Oand on the opposed outer peripheries of the wire 111 and 121 in suchregion X100. The control arrangements thus shown effect the desiredpredetermined pressures by acting against the inner peripheries of thetwo wires 111 and 121 in the region X- 100, coupled with adjustabledirection of the longitudinally unidirectional jet, i.e. along thecenterline CL100, so as to effect the desired conditions within theforming zone between the opposed outer peripheris of the wire 111 and121. The desired conditions of spacing between the wires 111 and 121 inaccordance with the formula previously disclosed herein is thus oneaspect of the control feature, but in the arrangement shown in FIG. 4A,the suction elements 126aa-126x and S115 will additionally cooperatewith each other to effect the relatively equal drainage in oppositedirections that is desired. The additional adjustable alignment of thejet stream centerline CL-100 serves to cooperate with such drainagedevices for the purpose of effecting a desired relative drainage ratebetween the two wires, also as previously described in connection withthe general concept of aligning the jet stream enterline CL-100 more orless tangentially with respect to the roll 26, as indicated in FIG. 2.

Because of the size of the open roll 126 and a predetermined selectionof the nature and character of the stock being used in the web W-100being formed, the embodiment of FIG. 4A demonstrates a highly simplifiedpaper forming arrangement wherein advantage is taken of a stock streamcenterline direction (IL-100 that is upward rather than horizontal ordownward, such that the travel of the wires in parallelism in thegeneral region PP on FIG. 4A (with the web W400 sandwiched therebetween)is required for a relatively short travel path.

It will be appreciated, however, that the length of the travel path inparallelism PP can be increased easily in the embodiment of FIG. 4A bymoving the position of the roll 113a peripherally over the top of theroll 126, if such is desired. Also, the jet stream delivering deviceJ-100 may be adjustably positioned with nominal changes being made inthe device of FIG. 4A so as to feed generally horizontally as well asgenerally tangentially along the bottom side of the roll 126, or evenalong a downwardly inclined side of the roll 126, although adjustmentsto this extent are not suggested as being possible with the specificadjusting devices herein designed J,,-100, J 100 and 1 -100. Instead,the overall arrangement of elements shown in the two different positionsof the FIG. 1 and the FIG. 4 series will demonstate to the workers inthe art certain essential features of versatility in the overallarrangement herein contemplated for excellent control of web formationin a high speed web forming device.

For example, in the arrangement of FIG. 4A, it will be appreciated thatwire guides shown in longitudinal succession include the upstreamcounterpart 115a to the element A in FIG. 2, as well as the lines ofcontact 115a shown in spaced longitudinal transverse alignment, whichmay be considered as a stationary water-permeable wire directioncontrolling guide. A second wire direction controlling it, of course,provided by the outer periphery of the open roll 126, and a third wiredirection changing guide in the embodiment of FIG. 4A is designated bythe guide roll 113a. Each of the guides just mentioned extendstransversely of the machine and the loops of the wires 111 and 121 whichpass over the first and second guides, respectively, and throughinitially closed spacing for receiving therebetween the jet streamaligned at CL-100. Substantially immediately upon receiving the jetstream a gradual convergence between the wires 111 and 121 is effectedby the opposed first guide means 115 and second guide means 126 in sucha web forming zone or zones X-100 and X-200, until the wires 111 and 121reach substantial or general parallelism PP with the resultant fibrousweb W100 therebetween, and which parallelism the wires 111 and 121travel longitudinally downstream over a portion of one of the initialguide means, i.e. the roll 126, and toward a third guide element, whichhas been designated in this instance as the roll 113a. The wire 111 doestravel over the third guide means 113a herein shown, although theembodiment of FIG. 4A differs from that of FIG. 1B in that the webfollows the opposite wire 121 in FIG. 4A, whereas it follows the wire 11in FIG. 1B. In either case, however, the two initial guide ele ments,115 and 126 (or 15 and 26, respectively) comprise a rotary member withan open water receiving periphery about which one of the wire runs iswrapped throughout the forming zone, and a substantially noncircularlycurved stationary water-permeable surface for effecting gradualconvergence between the wire runs in the web forming zone, which is theembodiment of 15 or 115, in either case, constituting a substantiallynon-circularly curved surface for the wire 11 or 111. Such substantiallycurved surface in each instance is defined by the longitudinal contourof the locii of the lines of contact, designated generally 115a in FIG.4A but described as being along the tops of the elements of 15b, 156,etc. in FIG. 2, in each case such longitudinally spaced wire contactinggenerally transverse edges or lines of contact defining the hereinbeforedescribed substantially noncircularly curved surface actually in termsof a plurality of successive chords in longitudial contour. The formingwires 11 and 111 are maintained under sufficient tension in the twoarrangements here shown so that such essentially chord-like structuresbetween the lines of contact for the blade boxes 15 and 115 will besubstantially maintained in spite of pressure generation within theforming zone which might otherwise tend to cause the forming wire 11 or111 to pass through reversed curves intermediate the lines of contact.It will be appreciated that such curve reversas would actually result inexcessively greater wire contact with the stationary surfaces of theblades in the boxes 15 and 115 and thus result in greater wire wear anda tendency to lose control of pressures at one or both sides of thewires 11 or 111 in the forming zone. Hence, the higher tension operationemployed for the wire 111 is preferred and such wire is preferablyformed of a conventional metal woven forming wire, whereas the oppositeforming wire 121 or 21 may be a plastic wire or a conventional metalfiber-woven wire, since the porous forming belt or wire 21 or 121 can besupported very conveniently on the co-moving and substantiallyunyielding outer periphery of the open rolls 26 and 126. In eitherevent, the cooperating configurations of the open rolls 26 and 126 andthe boxes 15 and 115 is such that the'gradual convergence in the formingzone, when plotted as spacing between the wire runs against the distancedownstream in the forming zone defines an elongated curve with its radiiincreasing with increases in the downstream distance, such curve thuspreferably will conform to the definition of an elongated paraboliccurve, and preferably specifically that of the formula hereinbeforediscussed. The various water removal as well as positional structuralelements hereinbefore described are controlled mutually to effectrelative drainage ratios preferably within the ranges of about 3:7 to7:3, which represent the relative drainage volumes through the opposedwires in the forming zones X-1 and X100, and preferably also X-2 andX200.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

We claim as our invention:

1. In a device for forming a fiborus web from a dilute aqueoussuspension of entangled co-moving fibers exiting from a slice as ahigh-speed substantially longitudinally unidirectional ribbon-thinjet-stream, in combination,

spaced successive first, second and third transverse guides arranged todefine a smoothly curved upwardly directed path of travel in respect tosaid unidirectional jet-stream; and first and second opposedsubstantially transversely co-extensive porous forming belt runstraveling longitudinally substantially at the jet-stream speed (a) oversaid first and second guides, respectively, and through initially closespacing for receiving therebetween the jet stream, and (b) immediatelythereafter through a curved gradual convergence in a web-forming zoneand into general parallelism with a resultant fibrous formed webtherebetween in which parallelism said runs are maintained as theytravel longitudinally downstream over a portion of one of said first andsecond guides upwardly toward (c) said third guide, over which at leastone of said runs travels, said second guide being a rotary member withan open water-receiving periphery about which said second run is wrappedthroughout the forming zone, said first guide presenting to said firstrun a substantially non-circularly curved stationary water-permeablesurface for causing said gradual convergence between said runs in theweb-forming zone, said substantially non-circularly cured surface of thefirst guide being defined by the longitudinal contour of loci of amultiplicity of closely longitudinally spaced belt-contacting generallytransverse edges.

2. The device of claim 1 wherein said transverse edges terminateabruptly at their otf-runing sides relative to their stationary edgeportions contacting said first belt run traveling longitudinallythereover for substantially minimizing forming zone stock pressurevariation along said one belt.

3. The device of claim 2 wherein said first run travels under tensionover said first and third guides, and an additional guide maintainstension thereon.

4. The device of claim 1 wherein said first and second guides maintaingradual convergence and diminishing spacing between the first and secondruns downstream from such initially close spacing at the upstream end ofthe forming zone, whereat such initial spacing is substantially equal tothe thickness of the jet-stream being received in the forming zone.

5. The device of claim 4 wherein said first and second guideseffectively maintain substantially uniform pressure in the jet-streamwithin the forming zone.

6. The device of claim 4 wherein such spacing plotted against thedistance downstream from the upstream end of the forming zone definesubstantially the curve: H=CD wherein H is the spacing in inches, D issuch downstream distance in inches, C is a constant from substantially0.5 to 1.6 and k ranges from substantially 0.2 tog-0.8.

7. The device of claim 1 wherein said gradual convergence in the formingzone, when plotted as spacing between the runs against distancedownstream in the forming zone defines an elongated curve with its radiiincreasing with increases in the downstream distance.

8. The device of claim 1 wherein said gradual convergence in the formingzone, when ploted as spacing between the runs against distancedownstream in the forming zone defines an elongated parabolic curve.

9. The device of claim 1 wherein means are provided to align the slicerelative to entrance of the forming zone to maintain the ratio of waterremoved by the first run to that removed by the second run in suchforming zone with the range of about 3 :7 to 7:3.

10. The device of claim 1 wherein said second guide is provided with aninternal suction gland communicating with the open periphery thereofopposite the forminz zone for effecting a control of water removal fromthe forming zone via the second run.

11. The device of claim 1 wherein said first guide water-permeablesurfacehas at least substantially open area.

12. The device of claim 1 wherein means are provided for aligning theslice to feed the jet stream upwardly and into said forming zone alongthe uprunning side of said rotary open roll guiding the second run.

13. The device of claim 12 wherein said first run is defined by aforming wire consisting essentially of waterlubricated flexiblestretchable synthetic fibers.

14. The device of claim 12 wherein said first run travels wrapped aboutthe uprunning side of said open roll, in the aforesaid parallelism withsaid second run and means are provided adjacent the top of said rollwhereby said first run is separated from the open roll leaving the webtraveling over the top of the open roll on said second run.

References Cited UNITED STATES PATENTS 2/1948 Spencer 162(TFM) 5/1968Justus et a1 l62303 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3, 582, 467 Dated June 1, 1971 Inventor(s)DaVid R.Gustafson, john F. Schmaeng, John S. Finnila.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Col. 2, line 71 "well" should read will Col. 4, line 64 "(micro-finish)"should read (mirror-finish) Col. 5, line 32 "16f" should read 26f Col.8, line 40 "desired" should read desire Col. 8, line 48 "drainings"should read drainage Col. 9, lines 6-7, "avialable" should read--available Col. 9, line 9 "box" should read box 15 Col. 10, line 15"generallyy" should read generally Col. 10, line 16 "not shown)" shouldread --(not shown)--;

Col. 11, line 49 "increase" should read increased--;

Col. 13, line 72 "or" should read for Col. 14, line 14 "is" should readin Col 14, line 16 "the" should read a Col. 15, line 36*it" should readis--;

(Continued) Col. 16, line 67 "reeciving" should read receiving FORMPO-1050 HO-69l USCOMM-DC wane-Pee U S GOVERNMENT PRINTING OFFICE: IDBO-JGi-SSI UNITED STATES PA'l ENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3 582,467 Dated June 1 1971 PAGE 2 David R. Gustafson, John F.Schmaeng, Iohn S. Finnla.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

(Continued) line 72 "cured" should read "curved".

Co l8, line 8 "forminz" should read forming.

Signed and sealed this 11th day of January 1972.

SEAL) Attest:

.SDL'JARD MJ LEICIIER TR. ROBERT GOTTSCHALK (rttesting Officer ActingCommissioner of Patents i FORM 391050 uscoMM-oc SCENE-P69 U S GOVERNMENTPRINTING OFFICE 9'9 Q3l5*33l

